1. Field of the Invention
The present invention relates to the use of microcapsules comprising latent heat storage materials as capsule core in plasterboard, to the plasterboard in which they are present and to a process for producing this plasterboard.
2. Description of the Background
An important focus of research for reducing energy requirements and for utilizing available heat energy are latent heat storage materials. They have a variety of uses, for example as heat transfer media in heating and cooling systems or for the storage of heat in insulation materials or building materials. Their function is based on the enthalpy change associated with the solid/liquid phase transition, which results in absorption of energy from the surroundings or release of energy into the surroundings. They can thus firstly be used for keeping the temperature constant within a prescribed temperature range and, secondly, can improve thermal insulation in a suitable arrangement.
DE-A 19 654 035 describes microcapsules as heat transfer medium. In these, the storage medium is surrounded by a capsule wall of melamine/formaldehyde resin.
Melamine/formaldehyde resin microcapsules are likewise disclosed in U.S. Pat. No. 5,456,852, although these have a specific storage medium as core. However, such melamine/formaldehyde resin capsules display unsatisfactory hydrolysis stability over a prolonged period in the transport medium, which is generally aqueous.
U.S. Pat. No. 4,747,240 teaches the use, in gypsum plaster, of macroencapsulated storage substances which have a particle size above 1000 μm and whose capsule wall is a high-melting resin. However, capsules of this size require very thick walls to prevent them from being destroyed on mixing with the building materials.
EP-A-10 29 018 teaches the use of microcapsules having a capsule wall of highly crosslinked methacrylic ester polymer and a latent heat storage core in building cements/plasters. Thus, the microcapsules can be incorporated into gypsum plaster without influencing its properties.
An important building material is plasterboard. This is generally used in interior finishing of buildings for lining walls and ceilings. In this sector, too, there is a desire to increase thermal insulation and heat storage capacity. Such energy management is described in U.S. Pat. No. 5,501,268 which recommends plasterboard containing latent heat storage materials for this purpose. As latent heat storage material, a paraffin mixture is incorporated into the plasterboard. Precise details of the way in which it is added are not given.
U.S. Pat. No. 4,988,543 discusses the opportunities and problems in the incorporation of latent heat storage materials in plasterboard. Thus, macrocapsules could be located between the outer paperboard layers on the gypsum plaster mix. It is likewise possible for macrocapsules to be applied to the reverse side of the paperboard. It is conceivable that small spheres could be impregnated with latent heat storage materials and these spheres could be incorporated into the gypsum plaster mix or the latent heat storage materials could be mixed directly with the gypsum plaster mix. Finally, the entire, fabricated plasterboard could be impregnated with latent heat storage materials. U.S. Pat. No. 4,988,543 teaches that the use of capsules or spheres reduces the internal binding forces of the board. Likewise, processes in which the gypsum plaster is mixed directly with the latent heat storage materials are critical since adhesion problems with the paper also occur here. As a solution, U.S. Pat. No. 4,998,543 proposes spraying one side of the plasterboard with latent heat storage materials.
In the case of large areas of plasterboard which have been treated with unencapsulated latent heat storage materials, there is a risk of oil emissions into the air of the room. Furthermore, the latent heat storage materials in the liquid state start to flow slowly within the plasterboard, resulting in the long term in nonuniform distribution, in particular on the surface, known as “sweating”, which likewise has an adverse effect on the stability of the boards.